In a prior application, Ser. No. 407,829 filed Oct. 19, 1973, and now abandoned, a process was disclosed for forming fiber-reinforced foamed plastic articles such as glass fiber reinforced polyurethane articles. The present application discloses an apparatus for carrying out on a large commercial scale one aspect to that prior process invention. In U.S. Pat. No. 3,929,318, a mixer is disclosed for preparing foamed plastic precursors with fiber reinforcement immediately prior to dispensing that mixture into a mold where fiber-reinforced foamed plastic articles are formed. Both of these prior applications are related to the present application and are incorporated by reference herein.
The formation of large, flat fiber-reinforced panels in a one-step process is a unique operation, not heretofore carried out commercially. Accordingly, no significant prior art is known which is pertinent to the method and apparatus for forming such panels as to be disclosed herein. The most important problems to be met in producing these panels may be outlined as follows.
It is typical of such foamed plastic precursors that within thirty seconds after being mixed they begin to foam. Accordingly, in thirty seconds the mold into which the precursors are placed must be completely filled and closed. Thus, it is an essential feature of a mold for forming flat panels that it be filled very quickly and uniformly. In addition, such a mold must close quickly and at the same time avoid trapping air inside which could cause substantial defects in the panels which are produced. In this regard, it should be noted that in typical commercial application panels of approximately 10 feet .times. 45 feet and 1/4 inch and greater thicknesses can be produced. It will be appreciated that distribution of foamed material across such an extensive flat area can be a substantial difficulty in the formation of such panels. After filling, the mold must also be held closed against the force exerted by the foaming material in order to create a uniform panel. Since the material fills the mold cavity fully, adherence of the panel to the mold body may cause difficulties. It is essential that the mold be openable without damage to the panel.